Buyer due diligence · All · 10 min read
Engine Survey vs Hull Survey: Do You Need Both?
Budget $1,200 to $3,500 for combined surveys on heavy fiberglass twins and learn which findings belong in price negotiation versus insurance underwriting.
Last reviewed
Hull survey scope limits
Hull survey on $420,000 sportfish covers hull, deck, rigging overview, fuel systems visually, and sea trial observations—typically $1,100–$1,600 plus haul.
Surveyors note engine serials and hours but rarely borescope cylinders unless separately contracted—C-class engine risk can hide behind B-class hull pass.
Insurance and lenders accept SAMS/NAMS credentials for collateral—engine deep-dive is buyer optional unless lender specifies mechanical survey.
Moisture and steering findings from hull survey drive price credits; engine oil sheen noted without analysis is incomplete for $300k+ diesels.
Engine tech survey tools
Certified Cummins or CAT tech may charge $900–$1,800 per engine for borescope, compression, blow-by, and ECM download—$3,600 for quad-engine not uncommon.
Oil spectrographic analysis ($45–$90 per sample) detecting iron and copper trends predicts bearing wear—two samples showing copper spike justify $15,000 top-end budget.
Mercury outboard CDS fault history download reveals hidden overheat codes cleared before listing—worth $250 dealer pull on $350,000 twin outboard sale.
Mechanical survey findings become purchase agreement credits—$12,000 injector quote before closing beats post-close surprise.
When both are mandatory economics
Rule of thumb: both surveys when purchase exceeds $350,000, engines over 1,000 hours, or hull survey flags oil consumption over 1 quart per 10 hours.
Skip engine survey on low-hour gas I/O under $150,000—different risk profile than 1,200-hour diesels on $500,000 yacht.
Combined spend $2,800 on surveys versus 1% purchase price ($4,200 on $420,000) is normal due diligence band.
Schedule engine survey same sea trial day to correlate WOT data with borescope—saves second haul fee $450–$750.
Sources
- SAMS — Survey standards — Society of Accredited Marine Surveyors
- NAMSGlobal — Surveyor finder — National Association of Marine Surveyors
Questions
Will hull surveyor coordinate engine tech?
Sometimes—for fee; you often book mechanical survey separately with yard access.
Does insurance require engine survey?
Usually no unless speed or commercial use—lenders may require on older high-horsepower boats.
Can seller refuse engine borescope?
Yes—buyer then chooses walk-away or price risk; do not waive without credit for deferred mechanical inspection.